1. Technical Field
The present invention relates to a light-emitting apparatus and an electronic apparatus.
2. Related Art
In recent years, there is a need for a light-emitting apparatus which consumes less electric power and is reduced in weight growing in association with diversification of information apparatus. As one of such light-emitting apparatuses, an organic electroluminescence apparatus (hereinafter, referred to as “organic EL apparatus”) is known. The organic EL apparatus as described above generally includes a light-emitting element having a light-emitting layer between an anode (first electrode) and a cathode (second electrode). In addition, a configuration in which an electron hole injection/transport layer is arranged between the anode and the light-emitting layer and a configuration in which an electrode injection layer or a hole block layer is arranged between the light-emitting layer and the cathode are proposed to improve an electron hole injection property or an electrode injection property.
The organic EL apparatus described above has a problem such that the peak width of a spectrum of a light taken out from the light-emitting layer is wide, and the light-emitting luminance is low, so that sufficient color reproducibility cannot be obtained when it is applied to a display device. Therefore, a structure having a light-reflection layer formed between a substrate and the anode and the cathode being formed on a light-outgoing side of the light-emitting layer and having a transflective performance and includes an optical resonator structure which causes a light emitted from the light-emitting layer to resonate between the light-reflecting layer and the cathode is proposed.
In this configuration, the light emitted from the light-emitting layer reciprocates between the light-reflecting layer and the cathode, and only a light having a resonance wavelength corresponding to its optical length is amplified and taken out. Therefore, it is considered that a sharp light having a high luminance characteristic and a narrow spectrum is obtained.
However, the case of the organic EL apparatus in which the above-described optical resonator structure is employed has a problem such that when the spectrum width is reduced, the wavelength of the light shifts toward the low-wavelength side or the light-emitting luminance is lowered when a display surface is viewed obliquely, that is, with increase in angle of visibility, so that the light-emitting characteristic depends highly on the angle of visibility. Accordingly, as shown in International Publication No. 01/039554, a configuration which causes resonance with a certain degree of spectrum width by optimizing the optical length of a light emitted from the light-emitting layer is disclosed.
In recent years, further improvement of the angle-of-visibility characteristic is required in association with improvement of the quality of the organic EL apparatus.
FIG. 10 is a graph showing the angle-of-visibility characteristic of the light-emitting luminance in the related art. In FIG. 10, 0° on the vertical axis of an upper half portion represents the front in the direction of visual sense of a viewer (the direction of normal line of the display surface), that is, an angle of visibility of 0°. The light-emitting luminance is shown in a ratio in the case in which the light-emitting luminance is assumed to be 100% at a position of 0° in angle of visibility, and is shown on concentric circles with a center O representing 0% and an outermost circle representing 100%.
As shown in FIG. 10, in the related art, an optical length is optimized to achieve the highest light-emitting luminance at an angle of visibility of 0° for each of a red right R, a green light G, and a blue light B, respectively, so that an optimal white light W is emitted at an angle of visibility of 0°. The light-emitting luminance of each of R, G, and B is damped with increase in angle of visibility. In other words, the optical length is shifted from the optimal condition and is increased with increase in angle of visibility, and hence the light which is wanted to be taken out cannot be emitted under the condition of the optimal resonance wavelength. Accordingly, the peak wavelength of the spectrum of the light to be taken out is shifted to the lower wavelength side.
FIG. 11 is a chromaticity diagram showing the angle-of-visibility characteristic of the chromaticity in the related art. A solid line in this drawing shows a variation in peak wavelength of the spectrum in a case in which the angle of visibility is varied from 0° to 80°.
As shown in FIG. 11, in the related art, each of the red light, the green light, and the blue light is set to be emitted at an optimal chromaticity at positions of 0° in the angle of visibility (reference signs R1′, G1′, and B1′ in FIG. 11), so that the white light (reference sign W1′ in FIG. 11) is displayed. However, there is a problem such that when the peak wavelength of each color is shifted from the optimal condition toward the low-wavelength side (reference signs R2′, G2′, and B2′ in FIG. 11) with increase in angle of visibility as described above, an entire color shift is generated correspondingly. In other words, the white light is displayed at the position of 0° in angle of visibility, while it is shifted toward the blue side (low-wavelength side) with increase in angle of visibility and hence is viewed as a blue light (reference sign W2′ in FIG. 11).